<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style>
.one{font-family:宋体;font-size:15px;color:red;}
.two{font-family:宋体;font-size:20px;color:blue;}
.three{font-family:宋体;font-size:25px;color:green;}
</style>
</head>
<body>
<h2 class="one">应用选择器one</h2>
<p>你好</p>
<h2 class="two">应用选择器two</h2>
<p>我好</p>
<h2 class="three">应用选择器three</h2>
<p>大家好</p>
</body>
</html>